Electric resistance.



F. BULLING.

ELECTRIC RESISTANCE.

APPLIOATION FILED JUNE 20, 1912.

1,050,912, I Patented Jan.21, 1913.

"UNITED STATES PATENT OFFICE.

rnninmcmiaonmue, OF FRANKFORT-ON-THE-MAIN, GERMANY.

ELECTRIC RESISTANCE.

I type of electric resistances,especially used for heating purposes, inwhich a conductor formed by a metal wire or band is arranged on a sheetof insulating material capable of withstanding high temperatures. Suchresistances have, however, the drawback, that A, it becomes theconductor at the points where it is bent or folded is very liable toburn out and that further its different portions are easily displaced,thus coming in contact and forming short circuits. In order to avoidthese difficulties I employ clamps, which are clasped about the bendingpoints of the conductor, so that they protect the latter against burningout and secure it on the insulating sheet. Such clamps may further beemployed for greatly facilitating the building up of such electricresistances, which contain a metal band, especially if it is stamped outin zigzag form.

Further improvements will be readily understood from the followingspecification and the accompanying drawing, in which- Figures 1 and 2, 3and 4, three constructional forms each side view respectively.

In the first example (Figs. 1, 2) the conductor is a wire A wound arounda sheet B of suitable insulating material, for instance mica. If acurrent flows through the wire hot and its strength lessens. Also thesheet B is heated and tries to stretch itself. Thus partly by theheating of the wire in top and A, partly bythe stretching of the sheetB, the

employed as the bending" polnts of the conductor are'sub- 'jected to aheavy 'mechanical stress, so that they very easily break ortear, if theyare This is now done by the clamps C, which are clasped about the andthe edges of the insulating sheet. The

clamps further prevent the single pieces of the wire A from becomingdisplaced. In-

stead of a wire, a metal band could alse be conductor and wound aroundthe sheet B.

In the second example (Figs. 3, 4) the Specification of Letters Patent.

lating sheet length is to be left 5 and 6 show which were, however,bending points of the wire.

Patented Jan. 21,1913.

Application filed June 20, 1912. Serial- No. 704,873.

conductor is a thin metal. band A, which is cut into pieces. The clampsC not only mechanically secure these pieces on the insu- B, but formalso their electric connections. This construction has the furtheradvantage, that it is not necessary to first fold a comparatively longmetal band before it is secured on the insulating sheet.

If the ohmic value of resistances with a metal band as conductor is tobe high, without decreasing its thickness too much, the band is usuallystamped out in zig-zag form, as shown in Fig. 5. Such a band can,however, not be wound around an insulating sheet without certainprecautions, as otherwise the drawbacks set out above would result. Onthe other hand, if such stamped out bands are arranged only on one sideof an insulating sheet, great diiticulties are encountered in theprocess of making them, viz: The length of the different pieces must bein accord. with the respective purposes, and at both ends of such apiece, a certain Thus the mode of stamping such bands is verycomplicated, as the stamping machines, which work automatically and alsoautomatically feed or transport the band, are to be regulated fordifferent lengths. All these dii'liculties are easily overcome by againemploying the clamps C (Figs. 5, 6). Now it is possible to stamp out orto slit the band for its whole length without interruptions, and to cutit afterward into pieces of the requisite length. These pieces arearranged on one or both sides of the insulating sheet B and are securedby the clamps C, which also form the electric connections between theends of the single band pieces, The special advantage of thisconstruction is to be easily recognized from Figs. 5, 6 which show aheating resistance for a fiat iron, such as is used for ironing clothesand 'the like. For such a resistance there were previously employedthree diflerent lengths of a band stamped out in zig-zag form, the endsof not slotted, while acthe stamped out cording to my invention slotscan extend over the whole length of the band.

I In the first example (Figs. 1, 2) the conductor could also be arrangedon one side of the insulating sheet, and in the other examples (Figs.3-6) it could be arranged on both sides of it. In the first example thewithout stamped slots.

heat developed radiates from-both sides, and in the other forms onlyfrom one side of the resistance.

All the constructions are still. to be provided veying the current andcover. These elements are, however, not specified and illustrated, asthey do not form parts of my invention and could be constructed in anyknown or special manner.

I claim: v v

1. In an electric heating resistance the combination of a thininsulatingsheet of refractory niateral, a thin, flexible metal conductor arrangedto form a plurality of windings extending between opposite edges of saidsheet, and clamps of sheet metal clasped about the ends of each of saidwindings and the edges of the sheet, substantially as and for thepurpose described.

2. In an electric heating resistance the combination of a thininsulating sheet of refractory material, a'thin, flexible'metalconductor arranged to form a plurality of windshown and described withmeans for conwith an insulatlng ings consisting of separated piecesextending between opposite edges of said sheet, and clamps of sheetmetal clasped about the ends of each of said pieces and the edges of thesheet, substantially as and for the purpose described.

3. In an electric heating resistance the 'metal clasped about the endsof each of said pieces and the edges of the sheet, substan- I tially asand for the purpose described.

In testimony whereof I aflix my signature 1n presence of two witnesses.

FRIEDRICH BGLLING.

Witnesses:

JEAN GRUND, CARL GRUND.

